Hypervelocity gun



IMPLODED 25 2o \JOQ Sept. 9, 1969 c m 3,455,638

' HYPERVELOCITY GUN Filed Aug. 23, 1967 o HIGH EXPLOSIVE INITIATOR 2 5 PROPELLANT PROJECTILE GAS FIG. 5

DETONATION FRONT K TUBE I50 PROGRESSIVE TEST GAS IMPLOSION SHOCK FRONT FIG.2

ggumi- FIG. 3

INVENTOR. THOMAS N.CANNING BY 7 4M 5 C0 ATTORNEYS United States Patent 3,465,638 HYPERVELOCITY GUN Thomas N. Canning, Sunnyvale, Calif., assignor to the United States of America as represented by the Administrator of the National Aeronautics and Space Administration Filed Aug. 23, 1967, Ser. No. 662,828 Int. Cl. F41f 1/00, 17/00 US. Cl. 89-8 14 Claims ABSTRACT OF THE DISCLOSURE The hypervelocity gun of the present invention is an implosion-driven, light-gas gun, which comprises a launching tube that is made of suitable ductile or yieldable material and is closed at one end thereof. Disposed within the launching tube and spaced from the closed end thereof is a projectile to be propelled along the tube and away from the closed end thereof. Contained within the launching tube between the closed end thereof and the projectile to be propelled is a well-known light propellant gas. Surrounding the launching tube commencing at the closed end thereof and extending to the portion of the launching tube intermediate the location of the projectile before firing and the open end of the tube is a suitable high explosive charge. An initiator or detonator is disposed at the closed end of the launching tube to detonate the high explosive charge.

The initiator is fired to cause the high explosive charge to explode progressively along the exterior of the launching tube in the axial direction of the launching tube and away from the closed end of the launching tube to produce a continuously advancing detonation front. This action results in the radial direction implosion of the launching tube that is progressive in the axial direction thereof and toward the open end thereof. As a consequence thereof, the propellant gas is continuously compressed to produce a continuously advancing shock wave front which impinges on the projectile and reflects therefrom to propel the projectile along the launching tube in the axial direction thereof and toward the open end thereof. After the projectile has started to move, the detonation wave and the shock-wave system between the detonation wave and the projectile follow the projectile to substantially the end of the launching tube.

The invention described herein was made by an employee of United States Government and may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates in general to hypervelocity guns, and more particularly to an implosion-driven, lightgas gun.

Hypervelocity guns have employed a reservoir of compressible propellant gas to propel a projectile through a launching tube. However, such compressed gas is relattively stagnant so that its effectiveness in propelling a projectile is limited to relatively short distances in the launching tube. Such reservoirs of compressed gas is relatively static and has a relatively low speed of travel after the compression time. As a consequence thereof, a large pressure drop is present between the compressed gas and the projectile after the projectile has obtained a high velocity. There is no continuous acceleration of the reservoir of propellant gas after the projectile has attained a high speed.

An object of the present invention is to provide a hypervelocity gun wherein the acceleration of the projectile is sustained or increased after reaching a high velocity.

Another object of the present invention is to provide a hypervelocity gun in which acceleration of the projectile is achieved after attaining a high speed without structural damage to the projectile.

Another object of the present invention is to provide a hypervelocity gun wherein the explosive charge therefor detonates progressively along a launching tube to produce continuous compression of the propellant gas for propelling the projectile at higher velocities.

Another object of the present invention is to provide a hypervelocity gun wherein the propellant gas is continuously compressed to set up 'acontinuously advancing shock-wave system to impel the projectile at higher velocities.

Another object of the present invention is to provide a hypervelocity gun wherein the launching tube is radially imploded progressively in the axial direction thereof to continuously compress the propellant gas for irnpelling the projectile at high velocities.

Another object of the present invention is to provide a hypervelocity gun wherein the compressed propellant gas is forced to advance along the launching tube at a high speed to accelerate the projectile along the launching tube.

Another object of the present invention is to provide a hypervelocity gun in which a continuously moving detonation front applies continuously additional energy and compressive force to the propellant gas for accelerating the travel of the projectile along a launching tube.

The hypervelocity gun of the present invention has a high explosive charge surrounding a ductile or yieldable launching tube which extends from a closed end of the launching tube to a portion of the launching tube between the location of the projectile before firing in the launching tube and an open end of the launching tube. Trapped between the closed end of the launching tube and the projectile is a compressible propellant gas. The high explosive charge is detonated and explodes progressively along the exterior of the launching tube in the axial direction and toward the open end thereof. This action causes a radial implosion of the launching tube progressively in the axial direction of the launching tube toward the open end thereof for continuously compressing the propellant gas to produce a continuously advancing shock wave front moving in the axial direction of the launching tube toward the open end thereof with the result that the projectile is propelled along the launching tube toward the open end thereof.

Other and further objects and advantages of the present invention will be apparent to one skilled in the art from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic longitudinal cross-sectional of the hypervelocity gun of the present invention before firing.

FIG. 2 is a diagrammatic longitudinal cross-sectional view of the hypervelocity gun shown in FIG. 1 during firing.

FIG. 3 is a diagrammatic longitudinal cross-sectional of a hypervelocity shock tube, which is a modification of the hypervelocity gun illustrated in FIGS. 1 and 2.

Illustrated in FIG. 1 is the hypervelocity gun 10 of the present invention, which comprises a launching tube or liner 15. Such a launching tube may be a missile launching tube or a gun barrel. At one end 15a thereof, the launching tube 15 is closed and at the opposite end 15b thereof, the launching tube 15 is open. The launching tube 15, which is of a cylindrical configuration, is made of a suitable ductile or yieldable material. It has been found that steel with a relatively high yield stress has been particularly suitable.

Disposed within the launching tube 15 for movement in the direction of an arrow 16 is a projectile or model 20. The projectile 20 may be a cylindrical or spherical solid body or a compact assembly of solid bodies which taken together to form a cylindrical assembly with a diameter slightly greater than the inner diameter of the launching tube 15 so that the projectile 20 may move along the launching tube 15 and yet having sealing en gagement therewith. The projectile 20 is initially placed at an appropriate distance away from the closed end 15a of the launching tube 15, such as fifty times the diameter of the launching tube 15.

Contained within the launching tube 15 between the closed end 1511 of the launching tube 15 and the projectile 20 is a suitable compressible, light propellant gas 25, such as helium or hydrogen. Surrounding the launching tube 15 is a suitable high explosive charge 30. The high explosive charge 30 has a cylindrical configuration and is disposed along the exterior wall of the launching tube 15. In the exemplary embodiment, the high explosive charge 30 is disposed adjacent to the closed end 15a of the launching tube 15. According to the present invention, the explosive charge 30 extends to a portion of the launching tube 15 that is located intermediate the location of the projectile 20 before firing and the open end 15b of the launching tube 15. In this regard, the forward end 30a of the explosive charge 30 is between the forward surface 20a of the projectile 20 before firing and the open end 1512 of the launching tube 15.

At the closed end 1511 of the launching tube 15 is mounted a conventional initiator or detonator 35. The detonator 35 serves to fire or explode the explosive charge 30. For this purpose, a suitable electrical line 36 is connected to equipment, not shown, for operating the detonator 35. At the forward end of the launching tube 15, a vacuum is created (FIG. 1) in order to reduce the resistance to acceleration of the projectile to a minimum.

The implosion-driven, light-gas gun of the present invention effects a controlled acceleration of the projectile 20 to achieve high velocities in the order of 40,000 feet per second without structural damage to the projectile 20. In this manner, a study may be made or research may be performed to determine the reactions of space vehicles to their environment while in space and while travelling through atmospheres.

In the operation of the hypervelocity gun or implosiondriven, light-gas gun 10 of the present invention, the projectile 20 is placed within the launching tube an appropr1- ate distance from the initiator 35 with a light propellant gas trapped between the closed end a of the launching tube 15 and the projectile 20. The forward end of the launch tube is subject to a vacuum state. The initiator or detonator 35 is fired in a well-known manner. As a consequence thereof, the explosive charge 30 explodes progressively from the closed end 15a of the launching tube 15 in the axial direction thereof and toward the open end 15b of the launching tube 15. This action produces a resulting annular and planar detonation front 30b (FIG. 2), which advances in the direction of the arrow 16 through the high explosive charge 30 surrounding the launching tube 15. The resulting planar detonation front 30b, in turn, causes the launching tube 15 to implode radially and progressively in the direction of the arrow 16 as shown in FIG. 2.

The implosion of the launching tube 15 produces a chain of strong hydrodynamic shock waves from the continuous compression of the trapped propellant gas 25. The chain of shock waves results in a continuously advancing shock front 25a which moves alternately from the implosion front to the projectile and returns. With the impact of the first shock wave at the closed end 15a of the launching tube 15, the projectile accelerates along the launching tube 15 in the direction of the arrow 16. The pressure drop at the trailing surface of the projectile 20 resulting from the acceleration thereof is repeatedly minimized or offset by the continuously moving shock wave system 25a produced continuously in the light compressed propellant gas 25. After the projectile 25 exceeds the detonation velocity of the high explosive 30, the average pressure at the trailing surface of the projectile 20 begins to drop. The acceleration of the projectile 20 continues, however, to higher projectile speed as the compressible, light propellant gas expands to low pressure.

From the foregoing, it is to be observed that in the present invention, the high explosive charge 30 explodes progressively along the launching tube 15 to implode radially and progressively along the launching tube 15 to set up through the propellant gas 25 a continuously moving shock wave system 25 that travels at very high velocities back and forth in the propellant gas 25 to continuously exert a propelling force on the trailing surface of the projectile 20 to propel the projective 20 along the launching tube 15 in the direction of the arrow 16. Hence, the implosion-driven, light-gas gun 10 can effect acceleration of the projectile 20 without structural damage thereto up to velocities of 40,000 feet per second.

During the initial acceleration of the projectile 20, the detonative wave 3% and the shock wave front 25a will be moving at a higher speed than the projectile 20 and the pressure between the imploded portion of the launching tube 15 and the projectile 20 may be sufficiently high to tend to rupture the launching tube 15. In such an event, the launching tube 15 may be reinforced by heavier Walls at the critical locations.

Illustrated in FIG. 3 is a modification of the hypervelocity gun shown in FIGS. 1 and 2 for use as a driver 40 for a shock tube. In this regard, the driver 40 comprises a ductile or yieldable tube or barrel 45, which includes an open end and a closed end. At the closed end of the tube 45a is located an initiator or detonator 50, which operates in the same manner as does the detonator 35. In lieu of a model or projectile, such as the projectile 20, the driver member 40 employs a diaphragm 55 of minimum weight. The diaphragm 55 is in sealing engagement with the tube 45. Between the diaphragm 55 and the closed end of the tube 45 is a supply of compressible, light propellant gas 60. At the forward side of the diaphragm 55 is located a driven tube 46 containing a supply of selected test gas to furnish a desired atmosphere at a selected pressure to fit the needs of an experiment or research project. Surrounding the exterior of the tube 45 is a suitable high explosive charge of a cylindrical configuration. The high explosive charge 70 commences from the closed end of the tube 45 and terminates at a portion of the tube 45 between the closed end thereof and the diaphragm 55. The diaphragm 55 is made of a suitable material, such as Mylar, that will be puncturable but yet will not contaminate pure gas. It is apparent that metallic material, such as aluminum, may be employed equally as well.

In operaion, the initiator or detonator 50 is fired and the explosive charge 70 explodes progressively from the closed end of the tube in the axial direction thereof and toward the open end of the tube. This action produces a resulting plane detonation front which advances in the direction of an arrow 71 through the tubular explosive charge 70 surrounding the tube 45. The resulting plane detonation front, in turn, causes the tube 45 to implode radially and progressively in the direction of the arrow 71. It is desirable to implode the portion of the tube containing the propellant gas 60 at a constant rate. Stated otherwise, the speed of travel of the detonation front should be constant.

The implosion of the tube 45 produces a single strong hydrodynamic shock wave from the continuous compression of the trapped propellant gas 60. When the first shock wave in the propellant gas 60, produced by the progression implosion of the tube 45, ruptures the diaphragm 55, the propellant gas 60 expands into the driven tube 46 containing the test gas. The resulting shock wave in the test gas produces a high thermal energy state by physical shock compression. By virtue of this action, the qualities of the test gas may be studied under conditions ditficult to achieve by any other method.

It is to be understood that modifications and variations of the invention disclosed herein may be resorted to without departing from the spirit of the invention and the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to protect by Letters Patent is:

1. A hypervelocity gun comprising a ductile tube, an explosive charge surrounding said tube and extending in the longitudinal direction of said tube, said tube comprising a closed end portion and an open end portion, detonator means disposed adjacent the closed end portion of said tube for firing said explosive charge to cause said explosive charge to explode progressively along said tube in the longitudinal direction of said tube and toward the open end portion of said tube for imploding said tube progressively in the longitudinal direction of said tube toward the open end portion of said tube, a projectile disposed within said tube for movement along said tube in the longitudinal direction, said charge being substantially longer than said projectile, said projectile, before said charge is fired, being near said closed tube portion and said charge extending beyond both longitudinal ends of said projectile, and a supply of propellant gas disposed in said tube between the closed end portion of said tube and said projectile, said propellant gas being continuously compressed and impelled by the progressive implosion of said tube to propel said projectile along said tube in the longitudinal direction thereof and toward the open end portion thereof.

2. A hypervelocity gun as claimed in claim 1 wherein said explosive charge has a cylindrical configuration and when fired produces a continuously advancing detonation front moving in the longitudinal direction and toward the open end portion of said tube for imploding said tube progressively in the longitudinal direction and toward the open end portion of said tube.

3. A hypervelocity gun as claimed in claim 1 wherein said tube is imploded radially and progressively in the longitudinal direction to continuously compress said propellant gas for producing a continuously advancing shock wave system moving in the longitudinal direction toward the open end portion of said tube to propel said projectile in the longitudinal direction and toward the open end portion of said tube.

4. A hypervelocity gun as claimed in claim 2 wherein said tube is imploded radially and progressively in the longitudinal direction to continuously compress said propellant gas for producing a continuously advancing shock wave system moving in the longitudinal direction toward the open end portion of said tube to propel said projectile in the longitudinal direction and toward the open end portion of said tube.

5. A hypervelocity gun as claimed in claim 1 wherein said propellant gas is a light gas.

6. A hypervelocity gun as claimed in claim 4 wherein said propellant gas is a light gas.

7. A hypervelocity gun as claimed in claim 1 wherein said projectile is in sealing engagement with said tube to contain the propellant gas between the closed end portion of said tube and said projectile.

8. A hypervelocity gun as claimed in claim 6 wherein said projectile is in sealing engagement with said tube to contain the propellant gas between the closed end portion of said tube and said projectile.

9. A hypervelocity gun as claimed in claim 2 wherein said detonation front is a planar detonation front.

10. A hypervelocity gun as claimed in claim 4 wherein said detonation front is a planar detonation front.

11. A hypervelocity gun as claimed in claim 9 wherein said planar detonation front has an annular configuration.

12. A method of propelling a projectile along tube comprising the steps of, progressively firing an explosive charge in the longitudinal direction of the tube to produce a continuously advancing detonating front moving in the longitudinal direction of the tube, imploding the tube progressively in the longitudinal direction of the tube through the action of the continuously advancing detonation front, compressing continuously and moving all of the propellant gas contained in the tube through the progressive implosion of the tube to produce a continuously advancing shock wave front beyond the situs of the projectile prior to the firing of the explosive charge, and propelling the projectile along the tube in the longitudinal direction under the action of the coninuously advancing shock wave front.

13. In combination, a ductile tube, an explosive charge surrounding said ductile tube and extending in the longitudinal direction of said ductile tube, said ductile tube comprising a closed end and a diaphragm end portion, detonator means disposed adjacent the closed end of said ductile tube for firing sad explosive charge to cause said explosive charge to explode progressively along said ductile tube in the longitudinal direction of said ductile tube and toward the diaphragm end portion of said ductile tube for imploding said ductile tube progressively in the longitudinal direction of said ductile tube toward the diaphragm end portion of said ductile tube, a diaphragm disposed at the diaphragm end portion of said ductile tube, a supply of propellant gas contained by said ductile tube between the closed end thereof and said diaphragm, a coaxial tube on the opposite side of said diaphragm from said ductile tube, a supply of test gas in said coaxial tube, said implosion of said ductile tube compressing said propellant gas continuously to produce a shock wave for rupturing said diaphragm, whereby said propellant gas expands into said coaxial tube containing said supply of test gas.

14. The combination as claimed in claim 13 wherein said explosive charge has a cylindrical configuration to produce a detonation front advancing at a constant velocity to implode said ductile tube at a constant rate in the longitudinal direction toward the diaphragm end portion of said ductile tube.

References Cited UNITED STATES PATENTS 3,054,329 9/1962 Willig 89-8 3,204,527 9/1965 Godfrey et al. 898 3,295,412 l/1967 Morley et al. 89-8 3,056,336 10/1962 Tailer 891 X SAMUEL W. ENGLE, Primary Examiner US. Cl. X.R. 89-14 

